The invention relates to a casing for a spiral cable for connecting electrical line terminals between a stationary steering column and a steering wheel shaft. The steering wheel shaft is rotatably mounted in the stationary steering column and equipped with a steering wheel for a motor vehicle. The casing comprises two coaxial casing parts, which can be rigidly connected, in the one case as stator to the fixed steering column and, in the other case, as rotor to the steering wheel shaft and which are so shaped that, when functionally associated with one another, they form a coaxial annular space for the spiral cable.
A casing of this kind is known from EP O 417 350 Al. The casing pan forming the stator has an annular configuration and contains an annular space which is radially open towards the center. This opening is closed by the second casing part serving as rotor and held rotatably in the stator. The annular casing part therefore turns, when functionally associated with the steering wheel, in the stationary outer casing part associated with the steering column.
An object underlying the invention is that of providing a casing for a spiral cable, of the type first defined above, in which the two casing parts, when functionally associated on the one hand with a rotatable steering wheel and on the other hand with a fixed steering column, can be turned relative to one another substantially without friction and therefore silently.
This object is achieved through the fact that one of the two casing pans has a recess which forms the annular space and which is open towards an axial face of the casing part, and that the other casing part is in the form of a plate and radially covers the annular space. It is thus possible for the one casing part to be disposed at an axial distance from the other casing part, because the two casing parts are separated from one another. As soon as the one casing part is rigidly connected to the rotatable steering wheel shaft and the other is fastened, coaxially to the axis of the steering wheel shaft, to the stationary steering column, the relationship of stator to rotor performs the function of bearing the steering wheel shaft. The two casing parts are therefore associated with one another on installation in the steering unit, without being in contact with one another. Frictional noise, which in the prior art is caused by the rotation of the rotor casing in the stator casing, is thereby avoided. Because of the lower moment of friction of the steering unit, the latter also acquires more favorable torque.
As a development of the invention, the casing part provided with the annular space can be rigidly connected to a steering column tube. This casing part thus serves as stator. Since in a motor vehicle steering unit the stator is usually situated below the steering wheel, it is advantageous to use the casing part containing the annular space as stator, because in this case the conductor strip of the spiral cable is always situated in the annular space because of its own weight. In the reverse arrangement it would be possible for the conductor strip to become jammed in the radial gap between the two casing parts.
As a further development of the invention the plate-like casing part can be fixed on a steering wheel hub and has an axially projecting centering pin which can be centered in a corresponding recess in the steering wheel. This constitutes a particularly simple functional connection of the casing part to the steering wheel and therefore to the steering wheel shaft, because the casing part has only to be fixed to the steering wheel, so that, when the steering wheel is subsequently fastened on the steering wheel shaft, it will automatically be disposed concentrically to the steering wheel shaft.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.